Sealing a fiber bundle end with glass fritting

ABSTRACT

An apparatus comprises a housing having a first melting temperature and a fiber bundle extending through the housing. The fiber bundle comprises a plurality of fibers having a second melting temperature. An end of each of the plurality of fibers extends past an edge of the housing. The apparatus further comprises a first seal between the plurality of fibers themselves and a second seal between the plurality of fibers and an inner surface of the housing. The seals each comprise a glass material having a third melting temperature lower than the first two melting temperatures. The second seal is configured to be formed as a result of the fiber bundle being inserted into the housing. The glass material coats a tip of each of the plurality of fibers and at least a portion of a side of each of the plurality of fibers near an end of the fiber bundle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/956,942 filed Apr. 19, 2018 which claims the benefit of U.S.Provisional Application 62/488,118 filed Apr. 21, 2017, all of which areincorporated by reference herein in their entirety.

FIELD

The present disclosure is directed to medical devices and methods formanufacturing medical devices. More particularly, the present disclosureis directed to systems and methods for sealing an end of an opticalfiber bundle using glass fritting.

BACKGROUND

Fiber optic bundles may be used in various applications that involve thetransmission of light. A fiber optic bundle is an assembly of multipleoptical fibers, each of which is capable of transmitting light from oneend of the optical fiber to the other end. Many different types ofmedical instruments use fiber optic bundles for illumination, imaging,or both. An endoscope is one example of a medical instrument that usesfiber optic bundles. For example, an endoscope may be used to lookinside the body at a particular internal organ. The endoscope mayinclude a fiber optic bundle for directing light towards the internalorgan. The endoscope may also include a fiber optic bundle for capturingand carry an image of the internal organ to an eyepiece or some othertype of image viewer.

Assembling multiple optical fibers to form a fiber optic bundletypically includes terminating the optical fibers at an end of the fiberoptic bundle. As one example, a fiber optic bundle may be terminated bypotting the optical fibers with a polymer adhesive. The polymer adhesiveis cured to hold the optical fibers together and form a barrier at theend of the fiber optic bundle. Further, a sterilization cleaning processmay be performed on the fiber optic bundle. This sterilization cleaningprocess typically involves multiple autoclave cycles that produce heatand steam that can cause the polymer adhesive to break down.Consequently, currently available polymer adhesives may not provide abarrier with the level of leak-tightness or illumination performancethat is desired. Thus, improved systems and methods for terminatingfiber optic bundles are desirable.

SUMMARY

In one illustrative embodiment, a method comprises applying a fritmaterial to a plurality of fibers in a fiber bundle. The frit materialhas a first melting temperature lower than a second melting temperatureof the plurality of fibers in the fiber bundle. The method alsocomprises heating the frit material at a temperature between the firstmelting temperature and the second melting temperature to bind the fritmaterial to the plurality of fibers without melting the plurality offibers in the fiber bundle and to create a seal between the plurality offibers.

In another illustrative embodiment, an apparatus comprises a fiberbundle and a frit material. The fiber bundle is comprised of a pluralityof fibers extending within the housing, wherein tips of the plurality offibers are exposed at an end portion of the housing. The frit materialforms a hermetic seal between the plurality of fibers and between thefiber bundle and an interior surface of the end portion of the housing.The frit material has a lower melting temperature than the plurality offibers in the fiber bundle.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory innature and are intended to provide an understanding of the presentdisclosure without limiting the scope of the present disclosure. In thatregard, additional aspects, features, and advantages of the presentdisclosure will be apparent to one skilled in the art from the followingdetailed description.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion. In addition, the present disclosuremay repeat reference numerals and/or letters in the various examples.This repetition is for the purpose of simplicity and clarity and doesnot in itself dictate a relationship between the various embodimentsand/or configurations discussed.

FIG. 1A is an illustration of a medical instrument in accordance with anillustrative embodiment;

FIG. 1B is an illustration of an enlarged view of an end of an elongatemember of a medical instrument in accordance with an illustrativeembodiment;

FIG. 2 is an illustration of an enlarged view of an end portion of alight guide in accordance with an illustrative embodiment;

FIG. 3 is an illustration of a frit material applied to a plurality offibers in a fiber bundle in accordance with an illustrative embodiment;

FIG. 4 is an illustration of a fiber bundle inserted within a housing inaccordance with an illustrative embodiment;

FIG. 5 is an illustration of a fiber bundle bound to a housing by a sealin accordance with an illustrative embodiment;

FIG. 6 is an illustration of a process for forming a seal between aplurality of fibers in a fiber bundle, depicted in accordance with anillustrative embodiment; and

FIG. 7 is an illustration of a process for forming a seal between aplurality of fibers in a fiber bundle in accordance with an illustrativeembodiment.

DETAILED DESCRIPTION

In the following description, specific details are set forth describingsome embodiments consistent with the present disclosure. Numerousspecific details are set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art that some embodiments may be practiced without someor all of these specific details. The specific embodiments disclosedherein are meant to be illustrative but not limiting. One skilled in theart may realize other elements that, although not specifically describedhere, are within the scope and the spirit of this disclosure. Inaddition, to avoid unnecessary repetition, one or more features shownand described in association with one embodiment may be incorporatedinto other embodiments unless specifically described otherwise or if theone or more features would make an embodiment non-functional. In someinstances well known methods, procedures, components, and circuits havenot been described in detail so as not to unnecessarily obscure aspectsof the embodiments.

The illustrative embodiments described below provide a method andapparatus for terminating a fiber bundle in a manner that improves theperformance of the fiber bundle. In particular, the illustrativeembodiments described below provide a method and apparatus forterminating a fiber bundle using a frit material. For example, an end ofthe fiber bundle may be potted using a frit material having a lowermelting temperature than the plurality of fibers in the fiber bundle butwith a similar coefficient of thermal expansion. The frit material maybe heated to create a seal between the plurality of fibers in the fiberbundle. When the fiber bundle is located within a housing, the fritmaterial may also be used to create a seal between the fiber bundle andthe housing. In one illustrative embodiment, the seal may be a hermeticseal.

In one illustrative embodiment, the frit material is a glass fritcomprised of glass particles. Using a glass frit to hermetically sealthe end of the fiber bundle may help prevent a decrease in the level ofleak-tightness and illumination performance of the potted end of thefiber bundle. For example, once heated, the glass frit may besufficiently durable to withstand high temperatures and pressure and toseal against liquids, steam, air, or biologic intrusions.

Referring to FIGS. 1A and 1B of the drawings, a medical instrument 100is depicted in accordance with an illustrative embodiment. In FIG. 1A,the medical instrument 100 is an image capture device 102 that may beused to medically inspect various internal body parts and cavities. Forexample, the image capture device 102 may take the form of an endoscopeused to capture images that can then be viewed by a human operator usingthe image capture device 102.

In one illustrative embodiment, the image capture device 102 may includea body 104, a light source 105, an elongated member 106, an eyepiece107, and an image recording device 109. The body 104 is typically keptoutside of the patient anatomy during the actual inspection. Theelongated member 106 may be at least partially inserted inside the bodysuch that a distal end 108 of the elongated member 106 is positionedrelative to a body part of interest. The elongated member 106 may berigid, flexible, articulated, partially flexible, or a combinationthereof. Although depicted as curved or bent for exemplary purposes, invarious embodiments elongated member 106 may be straight, angled,curved, or any combination thereof. Depending on the implementation, theelongated member 106 may be comprised of metal, plastic, a combinationof the two, or some other suitable material.

The elongated member 106 may include channels housing variouscomponents, which may include an illumination system 110. Theillumination system 110 may direct light from the light source 105 toilluminate the portion of the patient anatomy being inspected. In otherwords, the illumination system 110 may direct light towards the portionof the patient anatomy at which the distal end 108 of the elongatedmember 106 is pointing. In this illustrative embodiment, theillumination system 110 may include a light guide. In other embodiments,the illumination system 110 may include multiple light guides, one ormore other components, or a combination thereof.

The elongated member 106 may also house an optional imaging bundle 114.The imaging bundle 114 may include a fiber bundle that is used tocapture and convey an image to the image recording device 109 or to theeyepiece 107 for viewing by the human operator. The fiber bundle may be,for example, a fiber optic bundle comprised of a plurality of opticalfibers. The image recording device 109 may take the form of a camera orsome other type of image recording device.

In FIG. 1B, an enlarged view of the distal end 108 of the elongatedmember 106 is shown. As depicted, the elongated member 106 may houseother optional components, such as, for example, without limitation, anair tube 116, a water tube 118, a suction tube 120, a control wire 122,or a combination thereof. In other illustrative embodiments, theelongated member 106 may also house some other type of component, suchas, for example, a biopsy extraction device (not shown).

FIG. 2 is an illustration of an enlarged view of an end portion of anoptical apparatus 200. The optical apparatus 200 may be, for example,the illumination system 110 (e.g., the light guide) or the imagingbundle 114 in FIGS. 1A and 1B. The optical apparatus 200 includes afiber bundle 201, a housing 202, and a seal 204. The optical apparatus200 may extend within a channel of the elongated member 106 such thatthe housing 202 is positioned near the distal end 108 of the elongatedmember.

The fiber bundle 201 is comprised of a plurality of fibers 206, whichmay take the form of a plurality of optical fibers. Accordingly, thefiber bundle 201 may also be referred to as a fiber optic bundle.Depending on the implementation, each optical fiber in the plurality offibers 206 may be made from silica, glass, plastic, or some othersuitable material that allows the optical fiber to transmit lightbetween the two ends of that optical fiber. The plurality of fibers 206may include any number of optical fibers. For example, withoutlimitation, the plurality of fibers 206 may include tens, hundreds, orthousands of optical fibers.

The housing 202 may have an outer surface 208 and an inner surface 210.The fiber bundle 201 may be located within a channel 212 defined by theinner surface 210 of the housing 202. The channel 212 may have adiameter 213 that may also be referred to as an inner diameter orinternal diameter of the housing 202. In one illustrative embodiment,the housing 202 may be comprised of a metallic material.

As depicted at the end portion 214 of the housing 202, a clearance 216is present between the housing 202 and the fiber bundle 201. Thisclearance 216 may help with insertion of the fiber bundle 201 throughthe housing 202. In this illustrative example, the clearance 216 may bethe percentage difference between the diameter 213 of the channel 212formed by the housing 202 and an outer diameter 218 of the fiber bundle201. For example, the diameter 213 of the channel 212 may be greaterthan the outer diameter 218 of the fiber bundle 201 to provide asufficient clearance 216 between the fiber bundle 201 and the innersurface 210 of the housing 202. In one illustrative embodiment, theclearance 216 desired may be at least 1 percent. For example, when thefiber bundle 201 has an outer diameter 218 of about 2.35 millimeters,the channel 212 may have a diameter 213 that is at about 2.37millimeters or greater. In some illustrative embodiments, the clearance216 desired may be at least 2 percent, at least 5 percent, at least 10percent, or even up to about 30 percent.

The seal 204 is present near the end portion 214 of the housing 202. Theseal 204 may bind the plurality of fibers 206 to each other and to theinner surface 210 of the housing. The seal 204 may be a barrier betweenthe individual fibers of the plurality of fibers 206 and between theplurality of fibers 206 and the housing 202.

The seal 204 is created using a frit material. The frit material isheated to melt the frit material to bind the frit material to theplurality of fibers 206 and the inner surface 210 of the housing 202. Inthis illustrative embodiment, heating the frit material may be performedby firing the frit material to melt the frit material. Firing the fritmaterial creates the seal 204 binding the plurality of fibers 206 toeach other and to the inner surface 210 of the housing 202. In thismanner, the seal 204 may hold the plurality of fibers 206 in aparticular configuration relative to each other and to the housing 202.In this illustrative embodiment, the frit material may be a glass fritcomprised of glass particles that are sufficiently durable to withstandthe heating process. Further, the seal 204 formed by the glass frit maybe a hermetic seal that protects against liquid, steam, air, or biologicintrusion.

As depicted in this illustrative embodiment, the optical apparatus 200has a polished end 220. The polished end 220 of the fiber bundle 201 maybe formed by both a plurality of exposed tips 222 of the plurality offibers 206 and the seal 204. In this illustrative embodiment, the tip ofeach optical fiber in the plurality of fibers 206 of the fiber bundle201 is exposed to allow illumination from the tip.

FIGS. 3-5 are illustrations of steps that may be used to form the seal204 shown in FIG. 2.

Turning first to FIG. 3, an illustration of a frit material 300 appliedto the plurality of fibers 206 in the fiber bundle 201 is depicted inaccordance with an illustrative embodiment. As depicted, the fritmaterial 300 has been applied to the plurality of fibers 206 in thefiber bundle 201 to form a wetted section 302 of the fiber bundle 201.In some instances, the wetted section 302 may also be referred to as acoated section.

The frit material 300 may have a lower melting temperature than theplurality of fibers 206. Further, the frit material 300 may have a firstcoefficient of thermal expansion that is within a predetermined range ofa second coefficient of thermal expansion of the plurality of fibers206. For example, without limitation, the plurality of fibers 206 andthe frit material 300 may have coefficients of thermal expansion thatare within a predetermined range of each other and between about 4×10⁻¹⁰K⁻¹ and about 9×10⁻¹⁰ K⁻¹. For example, the first coefficient of thermalexpansion for the frit material 300 may have a value that is betweenabout 4×10⁻¹⁰ K⁻¹ and about 9×10⁻¹⁰ K⁻¹ and that value may be within 1percent, within 2 percent, within 5 percent, or within some otherpredetermined range of the second coefficient of thermal expansion ofthe plurality of fibers 206.

The frit material 300 may be applied to the plurality of fibers 206 in anumber of different ways. In one illustrative embodiment, the fritmaterial 300 may be injected between the plurality of fibers 206. Inother illustrative embodiments, the frit material 300 may be painted orbrushed between the plurality of fibers 206.

In some cases, the frit material 300 may be mixed with a binder, asolvent, or both prior to applying the frit material 300 to theplurality of fibers 206. For example, the frit material 300 may be mixedwith a binder to form a paste that may be more easily applied to theplurality of fibers 206. As another example, the frit material 300 maytake the form of a powder that is mixed with a solvent, such as alcohol.The alcohol may be, for example, without limitation, isopropyl alcohol.The isopropyl alcohol may help in applying the frit material 300 to theplurality of fibers 206 because the surface tension of the isopropylalcohol may help wick the particles of the frit material 300 between theplurality of fibers 206.

The length of the wetted section 302 of the fiber bundle 201 may beselected to ensure that a proper seal is formed between the plurality offibers 206 and between the plurality of fibers 206 and the housing 202shown in FIG. 2. As one illustrative example, the frit material 300 maybe applied such that the wetted section 302 of the fiber bundle 201 hasa length substantially equal to or greater than the diameter of thefiber bundle 201. For example, when the fiber bundle 201 has a diameterof about 3.2 millimeters, the wetted section 302 of the fiber bundle 201may be at least about 3.2 millimeters or greater.

In some cases, the frit material 300 may be applied such that the wettedsection 302 of the fiber bundle 201 has a length that is at least about5 percent greater than the diameter of the fiber bundle 201. In othercases, the frit material 300 may be applied such that the wetted section302 of the fiber bundle 201 has a length that is at least about 10percent greater than the diameter of the fiber bundle 201.

In this illustrative embodiment, the plurality of fibers 206 may havesmall diameters. For example, without limitation, an optical fiber inthe plurality of fibers 206 may have a diameter of about 50 micrometers.In other illustrative embodiments, each optical fiber in the pluralityof fibers 206 may have a diameter of between about 20 micrometers andabout 80 micrometers (or larger or smaller diameters).

The frit material 300 may be selected such that the particles of thefrit material 300 have a size sufficiently small to allow the particlesto easily and readily disperse between the plurality of fibers 206. Inone illustrative embodiment, the frit material 300 may take the form ofa glass frit that is comprised of glass particles. In one illustrativeembodiment, the glass particles may have a diameter less than about 75micrometers. In some illustrative embodiments, the glass frit mayinclude glass particles with diameters ranging between about 5micrometers and about 70 micrometers. In one illustrative embodiment,the glass frit used may be SCHOTT GO18-255, which is manufactured by theSCHOTT Corporation.

Once the frit material 300 has been applied to sufficiently coat theindividual fibers and groups of fibers in the fiber bundle 201, thefiber bundle 201 may be ready to be inserted into the housing 202. Forexample, the fiber bundle 201 may be threaded into the channel 212 ofthe housing 202, beginning at the end portion 214 of the housing 202.

FIG. 4 is an illustration of the fiber bundle 201 inserted within thehousing 202, depicted in accordance with an illustrative embodiment. Thefiber bundle 201 with the wetted section 302 is inserted within thehousing 202 such that the plurality of fibers 206 protrudes past an edge400 of the end portion 214 of the housing 202. In particular, the fiberbundle 201 is inserted through the housing 202 such that at least aportion of the wetted section 302 of the fiber bundle 201 protrudes pastthe edge 400 of the housing 202.

For example, a first portion 401 of the wetted section 302 of the fiberbundle 201 may be located within the housing 202, while a second portion402 of the wetted section 302 may protrude past the edge 400 of thehousing 202. In one illustrative embodiment, the fiber bundle 201 may beinserted within the housing 202 such that the first portion 401 of thewetted section 302 that is located within the housing 202 has a lengthsubstantially equal to or greater than the outer diameter 218 of thefiber bundle 201. This length for the first portion 401 may help ensurethat a proper seal is formed at the end portion 214 of the housing 202.A proper seal may be formed when the migration of fluid or otherparticles into the optical apparatus 200 is prevented or limited towithin allowable tolerances. Further, the fiber bundle 201 may beinserted within the housing 202 such that a second portion 402 of thewetted section 302 that protrudes past the edge 400 of the end portion214 of the housing 202 has a length that is at least 1 percent greaterthan the diameter of the fiber bundle 201. This length for the secondportion 402 may help ensure that a seal is maintained at the end portion214 of the housing 202 after the exposed end portion 404 of the fiberbundle 201 is polished down.

The clearance 216 between the housing 202 and the fiber bundle 201 mayhelp with insertion of the fiber bundle 201 with the wetted section 302through the housing 202. As previously described, this clearance 216 maybe the percentage difference between the diameter 213 of the channel 212of housing 202 and an outer diameter 218 of the fiber bundle 201.

In some cases, after the fiber bundle 201 with the wetted section 302has been inserted through the housing 202, additional frit material 300may be applied to fill any gaps between the plurality of fibers 206 orbetween the fiber bundle 201 and the housing 202 at the end portion 214of the housing 202. For example, additional frit material 300 may beinjected, painted, or brushed between the plurality of fibers 206,between the fiber bundle 201 and the inner surface 210 of the housing202 at the end portion 214 of the housing 202, or both.

Although application of the frit material 300 to the fiber bundle 201prior to insertion of the fiber bundle 201 into the housing 202 has beendescribed, the frit material 300 may be applied after the fiber bundle201 has been inserted into the housing 202 in other illustrativeembodiments. For example, without limitation, the fiber bundle 201 mayfirst be inserted into the housing 202 and the frit material 300 theninjected, painted, or brushed between the plurality of fibers 206 andbetween the plurality of fibers 206 and the housing 202.

FIG. 5 is an illustration of the fiber bundle 201 bound to the housing202 by the seal 204, depicted in accordance with an illustrativeembodiment. The frit material 300 from FIGS. 3-4 may be heated to meltthe frit material 300 and create the seal 204. For example, melting thefrit material 300 binds the frit material 300 to the plurality of fibers206 and the inner surface 210 of the housing 202, binds the plurality offibers 206 together, and binds the plurality of fibers 206 to thehousing 202.

Creating the seal 204 may include performing various steps. In oneillustrative embodiment, the frit material 300 may be heated at a firstpredetermined temperature to off-gas any binders or solvents that weremixed in with the frit material 300. This first predeterminedtemperature may be, for example, between about 145 degrees Celsius andabout 300 degrees Celsius, depending on the type of frit material 300and the type of binder or solvent used. For example, the firstpredetermined temperature may be selected as sufficiently high tooff-gas any binders or solvents but below the melting temperature of thefrit material.

Once any binders or solvents have been sufficiently off-gassed, one ormore heating cycles may be performed. Each heating cycle may include,for example, without limitation, a firing step and a cooling step. Inother illustrative embodiments, each heating cycle may include only thefiring step.

The firing step includes firing the frit material 300 at a secondpredetermined temperature to bind the frit material 300 to the pluralityof fibers 206 and to the housing 202. This second predeterminedtemperature may be, for example, between about 470 degrees Celsius andabout 515 degrees Celsius, depending on the type of frit material 300.For example, the second predetermined temperature may be selected ashigher than the melting temperature of the frit material 300 butsufficiently below the melting temperature of the plurality of fibers206 to prevent any degradation of the plurality of fibers 206. As oneillustrative example, the frit material 300 may be fired using anautoclave oven set to a temperature of about 490 degrees Celsius forabout 15 minutes. This firing step causes the frit material 300surrounding the various individual fibers and groups of fibers in thefiber bundle 201 to melt and form the seal 204 that binds the pluralityof fibers 206 together and to the housing 202.

The cooling step of the heating cycle may include, for example, allowingthe seal 204 to be cooled such that the presence of any voids within theseal 204 may be identified. Depending on the implementation, the seal204 may be cooled actively using a device or passively without the useof any devices. If any voids are identified within the seal 204, theheating cycle may be repeated. Any number of heating cycles may beperformed until the seal 204 meets selected criteria for the seal 204.

In one illustrative embodiment, the selected criteria may include thatthe seal 204 is a hermetic seal 501 with no voids. The hermetic seal 501may prevent any liquid, air, steam, or biologic intrusion. In otherillustrative embodiments, the selected criteria may be that thepercentage of voids found within the seal 204 is less than a selectedthreshold. This selected threshold may be, for example, about 2 percentvoids. In other illustrative embodiments, the selected threshold may be0.5 percent voids. In still other illustrative embodiments, the selectedthreshold may be 0.01 percent voids.

Once the seal 204 has been properly formed, the exposed end portion 404(shown in FIG. 4) of the fiber bundle 201 near the end portion 214 ofthe housing 202 may be polished down to form polished end 220. Thispolishing may be performed using currently available polishing equipmentand currently known polishing processes. In this illustrativeembodiment, the polished end of the fiber bundle protrudes just past theedge 400 of the housing 202.

The illustrations of the medical instrument 100 in FIGS. 1A and 1B, thehousing 202 in FIGS. 1A, 1B, and 2 and FIGS. 4-5, the fiber bundle 201in FIGS. 2-5, and the frit material 300 in FIGS. 3-5 are not meant toimply physical or architectural limitations to the manner in which thedifferent illustrative embodiments may be implemented. Other componentsin addition to or in place of the ones illustrated may be used. Somecomponents may be optional.

For example, in some illustrative embodiments, the elongated member 106housing the light guide may house multiple light guides. In otherillustrative embodiments, the housing 202 may be comprised of a materialother than metal. Further, although the polished end 220 of the fiberbundle is shown protruding just past the edge 400 of the housing 202 inFIG. 5, the polished end 220 may be polished down to align with the edge400 of the housing 202 in other illustrative embodiments.

FIG. 6 is an illustration of a method for forming a seal between aplurality of fibers in a fiber bundle, depicted in accordance with anillustrative embodiment. The method 600 illustrated in FIG. 6 may beused to form a seal between a plurality of fibers, such as the seal 204formed between the plurality of fibers 206 in the fiber bundle 201described in previous figures. Although the seal may be formed at theend of a fiber bundle as previously illustrated, the method of thisdisclosure may be used (with or without polishing) to seal fiber bundleswithin fiber connectors, terminators or other optical fixtures. In someembodiments, the fibers of the fiber bundles may be sealed to oneanother without extending the fibers within a housing or otherterminating fixture. The method 600 is illustrated as a set ofoperations or processes 602-604. Not all of the illustrated processes602-604 may be performed in all embodiments of method 600. Additionally,one or more processes that are not expressly illustrated in FIG. 6 maybe included before, after, in between, or as part of the processes602-604. In some embodiments, one or more of the processes 602-604 areoptional and may be omitted.

The method 600 may begin with a process 602 that includes applying afrit material to a plurality of fibers in a fiber bundle, wherein thefrit material has a lower melting temperature than the plurality offibers and a first coefficient of thermal expansion within apredetermined range of a second coefficient of thermal expansion of theplurality of fibers. The frit material may be, for example, a glass fritthat is comprised of glass particles. The plurality of fibers may be,for example, a plurality of optical fibers. In process 602, the fritmaterial may be applied to the plurality of fibers in a number ofdifferent ways.

In one illustrative embodiment, the fiber bundle may be located within ahousing. The fiber bundle may protrude past an edge of an end portion ofthe housing. In other words, a tip of each of the plurality of fibers inthe fiber bundle may extend past an edge of the end portion of thehousing. In this example, the frit material may be injected between theplurality of fibers at the end portion of the housing to sufficientlycoat the plurality of fibers and form a barrier between the plurality offibers. Further, the frit material may be injected between the pluralityof fibers and an interior surface of the housing to form a barrierbetween the plurality of fibers and the interior surface of the housing.

In another illustrative embodiment, the frit material may be applied tothe plurality of fibers before the fiber bundle is inserted through thehousing. For example, the frit material may be injected or brushedbetween the plurality of fibers of the fiber bundle to form a barrierbetween the plurality of fibers. The fiber bundle may then be passedthrough the housing such that an end of the fiber bundle protrudes pastthe edge of the end portion of the housing. The frit material forms abarrier between the fiber bundle and the housing. If any gaps arepresent, additional frit material may be injected or brushed between theplurality of fibers at the end portion of the housing.

In still other illustrative embodiments, the fiber bundle is notinserted through any housing. Rather, in process 602, the frit materialis applied between the plurality of fibers of the fiber bundle andaround the fiber bundle to form a thick coating around the fiber bundle.

At process 604, the frit material is heated to bind the frit material tothe plurality of fibers and create a seal between the plurality offibers. In process 604, the frit material is heated at a temperaturethat is above the melting temperature of the frit material but below themelting temperature of the plurality of fibers.

In one illustrative embodiment, the heating in process 604 is performedby firing the frit material using an autoclave. With respect to process604, when the fiber bundle is located within a housing, firing the fritmaterial also binds the plurality of fibers to the housing. The fritmaterial has a lower melting temperature than the housing. Accordingly,in process 604, the frit material is fired at a temperature that isbelow the melting temperature of both the plurality of fibers and thehousing.

The frit material has a first coefficient of thermal expansion that iswithin a predetermined range of a third coefficient of thermal expansionof the housing. In one illustrative embodiment, the housing may becomprised of one or more metallic materials selected to provide a thirdcoefficient of thermal expansion for the housing within the desiredrange. For example, without limitation, the housing may be comprised ofa nickel-cobalt ferrous alloy, stainless steel, some other type of metalor metal alloy, or a combination thereof. The stainless steel may be,for example, 17-4 stainless steel, 420 stainless steel, or some othergrade of stainless steel. In one illustrative embodiment, when the firstcoefficient of thermal expansion for the frit material is between about4×10⁻¹⁰ K⁻¹ and about 9×10⁻¹⁰ K⁻¹, the third coefficient of thermalexpansion may be between about 5×10⁻¹⁰ K⁻¹ and about 12×10⁻¹⁰ K⁻¹.

FIG. 7 is an illustration of a method for forming a seal between aplurality of fibers in a fiber bundle, depicted in accordance with anillustrative embodiment. The method 700 illustrated in FIG. 7 may beused to form a seal between a plurality of fibers, such as the seal 204formed between the plurality of fibers 206 in the fiber bundle 201described in previous figures. The method 700 is illustrated as a set ofoperations or processes 702-718. Not all of the illustrated processes702-718 may be performed in all embodiments of method 700. Additionally,one or more processes that are not expressly illustrated in FIG. 7 maybe included before, after, in between, or as part of the processes702-718. In some embodiments, one or more of the processes 702-718 areoptional and may be omitted.

The method 700 may begin at a process 702 by mixing a frit material withat least one of a binder or a solvent. In one illustrative embodiment,the frit material may be mixed with isopropyl alcohol. In process 702,the frit material may be mixed with at least one of a binder or asolvent to form a paste that can be more easily handled.

Next, at process 704, the frit material is applied to a plurality offibers of a fiber bundle, wherein the frit material has a lower meltingtemperature than the plurality of fibers and a first coefficient ofthermal expansion within a predetermined range of a second coefficientof thermal expansion of the plurality of fibers. In process 704, thefrit material may be applied to the plurality of fibers by injecting,painting, or brushing the frit material between the plurality of fibers.In particular, the frit material may be applied to an end of the fiberbundle to coat a tip of each of the plurality of fibers with the fritmaterial and at least a portion of a side of each fiber near the end ofthe fiber bundle.

The frit material that is applied to the plurality of fibers may beselected based on an expected clearance between the fiber bundle and thehousing into which the fiber bundle is to be inserted. For example, thelower the expected clearance, the smaller the size of frit particlesthat may need to be used.

At process 706, the fiber bundle is inserted through a housing such thatthe tip of each fiber in the fiber bundle extends past an edge of an endportion of the housing and the frit material forms a barrier between thefiber bundle and an internal surface of the housing and between theplurality of fibers. At process 708, a determination may be made as towhether any gaps are present within the barrier. At process 710, if anygaps are present, additional frit material is applied to the pluralityof fibers at the end portion of the housing with the method thenreturning to process 708.

If no gaps are present, then at process 712, the frit material is heatedat a first predetermined temperature to off-gas any binders or. Inprocess 712, the frit material may be heated at a temperature between,for example, without limitation, about 140 degrees Celsius to about 160degrees Celsius. At process 714, the frit material is heated at a secondpredetermined temperature to bind the frit material to the plurality offibers and to the end portion of the housing to thereby create a sealbetween the plurality of fibers and between the fiber bundle and thehousing. In process 714, the frit material may be, for example, withoutlimitation, fired at a temperature between about 480 degrees Celsius andabout 500 degrees Celsius. The temperature and duration of firing maydepend on the type of frit material used.

At process 716, a determination is then made as to whether at least onevoid is present within the seal. If at least one void is present, themethod returns to process 714 described above. If no voids are present,then at process 718, the end of the fiber bundle is polished to form asurface in which a plurality of polished tips of the plurality of fibersare exposed, with the process terminating thereafter. In process 718,the polishing process may not reduce the performance or leak-tightnessof the seal beyond selected tolerances.

The method 600 described in FIG. 6 and the method 700 described in FIG.7 may be examples of the possible implementations for the apparatusesand methods in the illustrative embodiments. In alternativeimplementations, the steps described in these processes may occur out ofthe order shown. For example, without limitation, two steps shown insuccession may be executed substantially concurrently, the steps may beperformed in reverse order, or additional steps may be added.

While certain exemplary embodiments of the invention have been describedand shown in the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention. Additionally, it is to be understood that the embodiments ofthe invention are not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art.

Further, in the detailed description of the embodiments of theinvention, numerous specific details have been set forth in order toprovide a thorough understanding of the disclosed embodiments. However,it will be obvious to one skilled in the art that the embodiments ofthis disclosure may be practiced without these specific details. In someinstances, well known methods, procedures, and components have not beendescribed in detail so as not to unnecessarily obscure aspects of theembodiments of the invention.

What is claimed is:
 1. An apparatus comprising: a housing comprising ametallic material having a first melting temperature; a fiber bundleextending through the housing, wherein the fiber bundle is comprised ofa plurality of fibers having a second melting temperature, and whereinan end of each fiber of the plurality of fibers in the fiber bundleextends past an edge of an end portion of the housing; a first sealbetween the plurality of fibers themselves; and a second seal betweenthe plurality of fibers and an inner surface of the housing, whereineach of the first and second seals comprises a glass material having athird melting temperature that is lower than the first and secondmelting temperatures, wherein the second seal is configured to be formedas a result of the fiber bundle being inserted into the housing, andwherein the glass material coats: a tip of each fiber of the pluralityof fibers; and at least a portion of a side of each fiber of theplurality of fibers near an end of the fiber bundle.
 2. The apparatus ofclaim 1, wherein the plurality of fibers is a plurality of opticalfibers.
 3. The apparatus of claim 1, wherein the glass material is aglass frit.
 4. The apparatus of claim 3, wherein the glass frit has acoefficient of thermal expansion that is within approximately 1 percentand 5 percent of a coefficient of thermal expansion of the plurality offibers.
 5. The apparatus of claim 3, wherein the glass frit is mixedwith a binder or a solvent.
 6. The apparatus of claim 1, wherein each ofthe first and second seals is a hermetic seal.
 7. The apparatus of claim1, wherein an inner diameter of the housing is greater than an outerdiameter of the fiber bundle and a clearance distance extends betweenthe inner diameter of the housing and an outer diameter of the fiberbundle.
 8. The apparatus of claim 7, wherein the second seal extendsacross the clearance distance between the fiber bundle and the innersurface of the housing.
 9. The apparatus of claim 7, wherein theclearance distance is at least one percent of the inner diameter of thefiber bundle.
 10. The apparatus of claim 7, wherein the clearancedistance is at least ten percent of the inner diameter of the fiberbundle.
 11. The apparatus of claim 7, wherein the clearance distance isat least thirty percent of the inner diameter of the fiber bundle. 12.The apparatus of claim 1, wherein the end of the fiber bundle ispolished.
 13. The apparatus of claim 12, wherein the polished end of thefiber bundle extends past the edge of the end portion of the housing.14. The apparatus of claim 12, wherein the polished end of the fiberbundle is aligned with the edge of the end portion of the housing. 15.The apparatus of claim 1, further comprising a light source, wherein thefiber bundle is coupled to the light source.
 16. The apparatus of claim1, further comprising an image recording device, wherein the fiberbundle is configured to convey an image to the image recording device.17. The apparatus of claim 1, further comprising additional glassmaterial on the plurality of fibers located at the end portion of thehousing.
 18. The apparatus of claim 1, wherein each of the first andsecond seals further comprises a binding material mixed with the glassmaterial, wherein the binding material has a fourth melting temperaturelower than the third melting temperature of the glass material.
 19. Theapparatus of claim 18, wherein the binding material increases adistribution of the glass material among the plurality of fibers. 20.The apparatus of claim 1, wherein each of the first and second seals isfree of voids.